Process for spinning modified viscose solution



PROCESS FOR SPINNING MODIFIED VISCOSE SOLUTION Eugene Cameron Pontius,Chester, Va., assignor to E. I. du Pont de Nemours and Company,Wilmington, Del., a corporation of Delaware No Drawing. ApplicationAugust 16, 1954, Serial No. 450,255

3 Claims. (Cl. 106--165) This invention relates to the production ofartificial filaments, yarns and cords of regenerated cellulose by theviscose process. More particularly, the invention is concerned withimprovements in the process of spinning monoamine-modified viscose inthe production of rayon.

It has recently been discovered that marked improvements in rayonfilaments are obtained by adding monoamine modifiers to the viscosespinning solution or to the spinning bath. The modified filamentsobtained by spinning modified viscose solution under suitableconditions, as disclosed in U. S. Patent No. 2,535,044, issued December26, 1950, to Norman Louis Cox or spinning unmodified viscose intomodified baths as disclosed in U. 8. Patent No. 2,535,045; are readilydistinguished from unmodified rayon filaments by their smooth surfaces,i. e., the surfaces display no appreciable crenulation whereas theordinary filaments are highly crenulated. When dyed cross-sections areexamined under a microscope, the modified filaments are characterized byhaving considerably more skin than core, Whereas normal rayon is mostlycore with only a very thin skin. Yarn composed of these modifiedfilaments is denser than that from otherwise comparable unmodifiedfilaments, dyes more rapidly and, even more important, has markedlyimproved tenacity, fatigue resistance and abrasion resistance.Representative yarn and cord properties for filaments spun fromunmodified and modified viscose under otherwise comparable conditionsare as follows:

To is dry tenacity in grams per denier,

Tw is wet tenacity in grams per denier,

T1. is loop tenacity in grams per denier,

En is percent dry elongation,

To is conditioned tenacity in grams per denier Tom is oven-dry tenacityin grams per denier and D. B. fatigue is the number of minutes requiredto break the cord with the dynamically balanced fatigue tester.

These tests are conventional with the possible exception of the D. B.fatigue test. In this a cord is conditioned for 48 hours at 24 C. and54% relative humidity and clamped in jaws set 16.75 inches apart. A loadof 1 gram per denier is applied and the cord is brought to 100 C. whilein place in the machine for about one-half hour. The

jaws are then oscillated to stretch the cord 3,000 times per minuteusing a stroke of 0.24 inch.

The amine-modified viscose spinning solutions of the prior art, asdescribed in U. S. Patent No. 2,535,044, have been prepared by addingthe amine to completely xanthated alkali cellulose. When added in thisway, at least 1 millimole of amine per 100 grams of viscose is requiredfor the modifier to be efiective, and much larger amounts up to 10millimoles per 100 grams of viscose are usually required. The expenseinvolved in using such large amounts of modifier increases the cost ofthis rayon to an appreciable extent, and this is obviously undesirablein a commercial process.

smaller amounts of monoamine modifier than have previously been foundnecessary will be effective for producing rayon having the improvedproperties described above. Another object is to improve the process ofspinning monoamine-modified viscose spinning solution to provide rayonyarns and cords which exhibit a still further marked improvement inproperties. Other objects of this invention will become apparent fromthe following description and claims:

These objects are accomplished by splitting the Xanthation of alkalicellulose, so that not more than of the desired final Xanthation isaccomplished by the customary dry phase Xanthation with carbondisulfide, and then incorporating the monoamine modifier during a finalstage of Xanthation in which the partial xanthate is mixed with diluteaqueous caustic solution to a cellulose content of 4% to 15% and treatedwith carbon disulfide to complete the Xanthation. When the viscosesolution is prepared in this way a surprising reduction in the amount ofmono amine can be made. The amount added per grams of the final viscosesolution can be as little as about 0.02 millimole, or less, and not morethan about 1 millimole for any of the monoa'mines encompassed by thisinvention. For best results from 0.1 to 0.85 millimole per 100 grams ofviscose is preferred. A further unexpected result of this process isthat even better properties are obtained in the spun rayon.

The alkali cellulose used is prepared in the conventional manner, whichinvolves soaking sheets of wood pulp or cotton linter cellulose incaustic alkali solution, draining the caustic solution from thesaturated sheets, pressing excess caustic from'the sheets, shredding theresulting alkali cellulose and aging the alkali cellulose to provide thedesired viscosity in the viscose ultimately prepared.

The alkali cellulose is placed in a rotating drum called a baratte.Carbon disulfide is added and the baratte is rotated to provide mixing.Xanthation of the alkali cellulose occurs and is continued until anabsolute xanthate sulfur substitution value of at least 13% is obtained,based on the cellulose content of the material. However, only a partialxanthate sulfur substitution is to be achieved in this step, as theXanthation must be completed under different conditions in the presenceof the modifier. Based on the absolute xanthate sulfur substitutionvalue obtained in the final Xanthation, the Xanthation is split so thatnot over 90% of the xanthate sulfur substitution occurs in this firststep, e. g., if a final absolute Value of 27.0% is desired, the absolutexanthate sulfur substitution value at the conclusion of this first stepmust not exceed 24.3%. In order to avoid confusion, the propora measuredquantity of dilute aqueous caustic soda solu- Patented Oct. 22, 1957,

tion sufiicient to give a cellulose content of 4% to 15% and acellulose: caustic ratio approximating that of the final viscosesolution. Preferably the partial xanthate is added to a conventionalviscose mixer filled with the caustic solution in proportions giving acellulose content of 4% to 10% and a caustic content of 4% to 8% in thefinal mixture, mixed for about 5 to 30 minutes to dissolve the partialxanthate, and suflicient carbon disulfide is added to complete thexanthation. Other methods of accomplishing this part of the xanthationare disclosed in copending U. S. application Serial No. 351,592 ofAndrew Robertson, which is assigned to the assignee of the presentapplication.

The monoamine modifier should be incorporated into the viscose duringthe final stage of xanthation. For this purpose the addition of themodifier is preferably prior to or within twenty minutes after the startof the final xanthation reaction. The modifier may be added with thecaustic solution or with carbon disulfide for the final xanthation step,or may be added separately to the mixture. Suitable modifiers areorganic primary or secondary monoamines, i. e., having at least onehydrogen atom attached to the amino nitrogen, said amine having at leasttwo and preferably at least four carbon atoms, but containing no morethan eight carbon atoms in any one radical, and should be soluble to theextent of at least 0.1% in 6% caustic soda solution. Illustrative ofthese modifiers are cyclohexylamine, N-methylcyclohexylamine,N-ethylcyclohexylamine, diethylamine, morpholine andortho-methyl-N-methylcyclohexylarnine.

The resulting viscose solution is filtered, deaerated and may bepermitted to ripen at a temperature of about 18 C. The viscose is thenpumped to the spinning machine. The yarn fatigue resistance may beimproved by heating the viscose, as by means of a small oil-bath heatexchanger placed between the spinning pump and the spinneret. Heatingmay be accomplished with any suitable heating medium, such as steam, hotwater, oil, or coagulating bath; or an electric heating unit may beinserted in the pipe.

The viscose spinning solution, which may be heated before spinning,preferably to 4080 C., is extruded through a spinneret into acoagulating and regenerating bath maintained at a temperature from 40 C.to 80 C. and containing 4 to 12% sulfuric acid, 13 to 25% sodium sulfateand 2 to 15% zinc sulfate. The zinc sulfate is an essential component ofthe spinning bath. If desired, other divalent metal salts known toreinforce or supplement the action of zinc sulfate may also be used.These include ferrous sulfate, manganese sulfate, nickel sulfate orchromic sulfate. A spinning tube may be used as described in MillhiserU. S. Patent No. 2,440,057 to confine the filaments in their criticalstage of formation so that no substantial tension is imposed upon them.When spinning the monoamine-modified viscose of this invention, theconcentration in the spinning bath of modifier or reaction products withthe modifier will inevitably build up. Since it is ditficult todetermine the form of the modifier in the bath, this concentration issimply expressed in terms of parts per million of nitrogen. In order toobtain the results of my invention, it is important to maintain thislevel of modifier in the bath below about 200 parts per million ofnitrogen by extracting any excess during recirculation of the spinningbath. The bath may contain no nitrogen but in commercial practice it ismore likely tocontain between 20 and 200 parts per million. It has beenfound that the larger the concentration of nitrogen 4 in the bath, thesmaller the concentration of modifier required in the viscose.

After extrusion, the filaments are given a travel of 100- 250 inches inthe primary bath by means of a multiple roller set-up which graduallyapplies tension to the traveling filaments and thereby orients themwhile they are still plastic. The preferred method is to apply a part ofthe stretch beyond the primary bath in a secondary bath or between feedwheels. The secondary bath may consist simply of water or of dilute(14%) sulfuric acid, or it may be diluted coagulating bath. Thetemperature of the secondary bath is preferably between 50 C. and 100 C.Total stretches of -105% are preferred for producing high tenacity yarnsand 30105% for textile type yarns. From the last feed wheel, the yarn isfed into a rotating bucket to form a cake. The yarn is then washed andslashed. The slashing operation is well-known and consists of stretchingthe yarn and applying a lubricating solution. The process described isthe so-called bucket process. However, the bobbin process or any of thesocalled continuous processes may be used with similar results.

The invention will be more clearly understood by referring to theexamples below of preferred embodiments of the invention, and thediscussion which follows. In the tables of these examples the meaning ofthe symbols is as previously defined.

Example I Alkali cellulose, prepared from sheets of wood pulp in theconventional manner, was placed in a baratte. Thirty-two percent carbondisulfide (based on the weight of air-dried pulp) was added in thebaratte to achieve a xanthate substitution (percent xanthate sulfurbased on the cellulose present) of 21.7. The partially xanthated alkalicellulose was then fed into a mixer which contained dilute causticsolution and also contained cyclohexylamine. Twenty-five minutes later,7% carbon disulfide (based on the Weight of air-dried pulp) was added toproduce a total xanthate substitution of 27.1. Thus 80% of the totalxanthate substitution was accomplished during the first xanthation stepand the cyclohexylamine modifier was added prior to the secondxanthation step. The proportions were controlled to give a viscosesolution containing 6.25% by weight of cellulose, 5.75% sodium hydroxideand 0.049% cyclohexylamine (0.49 millirnoles of cyclohexylamine pergrams of viscose).

The viscose solution was filtered, deaerated and permitted to ripen to asalt index of 17.5 and to attain a viscosity of 29.5 stokes. Prior tospinning, the solution was passed through a coil-type heater immersed ina tank of hot water. The solution was heated to a temperature of about44 C. and then extruded into a bath maintained at 60.5 C. containing9.3% sulfuric-acid, 17.5% sodium sulfate, and 9.5% zinc sulfate. Thenitrogen content of the bath was maintained at 40-50 p. p. m. byremoving excess during recirculation of the bath.

The filaments were first led through a trumpet-like tube in the bath andthen, by means of tension rollers in the bath, they were stretched70-80%. After leaving the bath the filaments passed over two feed wheelsin succession having a differential in speed to stretch the filaments anadditional 20%. During this latter stretching, the filaments weretreated with diluted bath solution. The filaments were then led into arevolving bucket to form cakes. The cakes were purified, slashed andprocessed into tire cord in the conventional manner.

The following properties were obtained:

Yarn Properties Cord Properties Denier TD Tw T1. En Ew EL Denier To E151b.. Ton D. B.

Fatigue The example was re-run except that the viscose spinning solutionwas not passed through a heater prior to spinning. Similar results wereobtained as indicated by a product displaying in cross-section greaterthan 85% skin measured radially.

Example II A viscose spinning solution containing 6.25% by weightcellulose, 5.75% by weight sodium hydroxide and 0.07% by weightcyclohexylamine (0.7 millimole per 100 grams of viscose) was preparedfrom wood pulp sheets by a procedure identical to that described inExample I except for the amount of cyclohexylamine.

The solution had a salt index of 17.3 and a viscosity of 29.5 stokes. Itwas heated to 44 C. and spun into coagulating and regenerating bath at60.5 C. The composition of the bath and the ensuing treatments offilaments were those presented in Example I.

The following properties were obtained:

skin measured radially.

Example IV A viscose spinning solution containing 6.25 by weight 10weight cellulose, 5.75 by weight sodium hydroxide and 0.024%N-methylcyclohexylamine (0.21 millimole per 100 grams of viscose) wasprepared from sheets of wood pulp according to the split xanthationprocess described in Example I.

The solution was heated to 44 C. and spun into the coagulating bath ofExample I. The subsequent processing of the filaments was essentiallyequivalent to that described in Example I.

Yarn Properties Cord Properties Em lbs. Ton

D. B. Fatigue The example was re-run except that the viscose spin- Thefollowing properties were obtained:

ning solution was not passed through a heater prior to spinning. Similarresults were obtained as indicated by a product displaying incross-section greater than 85 skin measured radially.

Example 111 A viscose spinning solution containing 6.25% by weightweight cellulose, 5.75 by weight sodium hydroxide and 0.049% by weightcyclohexylamine (0.49 millimole per 100 grams of viscose) was preparedby the split xanthation process of Example I. However, in this example28% carbon disulfide (based on the weight of air-dried pulp) was addedin the baratte to achieve a xanthate Yarn Properties Cord PropertiesDenier Tn Tw TL En Denier To Elam. Ton D. B.

Fatigue The example was re-run except that the viscose spinning solutionwas not passed through a heater prior to spinning. Similar results wereobtained as indicated by a product displaying in cross-section greaterthan 85% skin measured radially.

Example V Example I was repeated with 0.024% N-methylcylohexylamine inthe viscose, instead of the 0.049% cyclohexylamine, and with theaddition of suflicient N-methylcyclohexylamine to the spinning bath tomaintain a concentration of about 0.056%, corresponding to p. p. m.based on the nitrogen content of the bath.

The following properties were obtained:

Yarn Properties Cord Properties Denier T1) Tw TL ED Denier To E15 lbs.Tom D. B.

Fatigue The example was re-run except that the viscose spinning solutionwas not passed through a heater prior to spin- 60 ning. Similar resultswere obtained as indicated by a product displaying in cross-sectiongreater than skin measured radially.

Example VI A viscose spinning solution containing 6.25% by weight 65cellulose, 5.75 by weight sodium hydroxide and 0.044%

by weight N-methylcyclohexylamine (0.39 millimole per grams viscose) wasprepared from wood pulp sheets Yarn Properties Cord Properties Denier T'Iw T E E E1. Denier Tc E15 lbs. T D. B.

Fatigue 7 according to the split xanthation process described in ExampleI. The solution was heated to. 44 C. and ex truded into a bath at 63% C.containing 9.1% sulfuric acid, 17.5% sodium sulfate, 9.5% zinc sulfateand .008% N- was prepared from wood pulp sheets according to the splitxanthation process. Eighty percent of the xanthation occurred in thebaratte and in the mixer with a total of 41% carbon disulfide (based onthe air-dried methylcyclohexylamine. 5 pulp) used.

The filaments were stretched 110% and collected on a In this case, thecyclohexylamine was added after the bobbin. They were processed inaccordance with the carbon disulfide for the second xanthation step hadbeen conventional bobbin process. The following properties added. Thepartially xanthated alkali cellulose was fed were obtained: into themixer which contained dilute caustic solution.

Yarn Properties Cord Properties Denier Tn Tw Tr. ED Denier To E1511".Too B- Fatigue The example was re-run except that the viscose spin-Twenty-five minutes later, 7.4% carbon disulfide was ning solution wasnot passed through a heater prior to added. Ten minutes'after thisaddition of carbon disulspinning. Similar results were obtained asindicated by 0 fide, the cyclohexylamine was added.

a product displaying in cross-section greater than 85 The solution wasthen filtered, deaerated and permitted skin measured radially. to ripenslightly. Prior to spinning, the solution was Exam le VH heated to 44 C.and extruded, processed, etc., in the man- 17 ner described in ExampleI.

Morpholine and diethylamine, representative of com- The followingproperties were obtained: The yarn, in mercially accessible secondaryamines, were also tested cross-section, exhibited 85-90% skin, based onradial on a smaller scale (so-called blow case spinning). Avismeasurement.

Yarn Properties Cord Properties Denier 'In 'Tw Tr. En Denier Tc Emu. TonPercent D. B.

Conv. Fatigue cose spinning solution containing 6.25% by weight eellu-The example was re-run except that the viscosespinning lose, 5.75% byweight sodium hydroxide was prepared solution was not passed through aheater prior to spinby the split xanthation process, as described inExample ning. Similar results were obtained as indicated by a I, using37% carbon disulfide. Eighty percent of the product displaying incross-section greater than 85% total xanthate sulfur substitution waspermitted to occur skin measured radially. in the first xanthation step.In one case, 0.05% by Weight The following monoamines were substitutedfor cycleof morpholine (0.57 millimole per 100 g. viscose) washexylamine in the processes described in Example I: used. In the secondcase, the viscose spinningsolution 9. n-Amylamine 14. Pyridine b% zi ggg gggg gig g g gzg g 10. N-butylethanolamine 15. Piperidine 6p e p g n11. Diethanolamine 16. Ortho-methyl,N-methyland processing followed, ingeneral, the operatlons de- 1 scribed in Exam le I exce t that no nitroen built u in Ethylethanolamme cyclohexylamme p P g p 13.N-ethylcyclohexylamine l7. Ortho-methyLN-ethylcythe spinning bath.

clohexylamme A filament having a smooth cross-section and composed 50 offrom 95 to 100% skin was obtained in both cases. The following physicalproperties were also obtained:

In all cases, the filaments produced had cross-sections which displayedmore than skin measured radially.

The example was re-run except that the viscose spinning solution was notpassed through a heater prior to spinning. Similar results were obtainedas indicated by a product displaying in cross-section greater than skinmeasured radially.

Example VIII A viscose spinning solution containing 6.25% by weightcellulose, 5.75 by Weight sodium hydroxide and .05 6% cyclohexylamine(0.56 millimole per grams viscose) 75 Since this quantity of skin hadproduced the excellent properties in the yarns and cords of thisinvention, this was considered to be sufficient evidence that the abovemonoarnines could be used with similar results in the process of myinvention.

Preferred primary and secondary monoamine modifiers for the purpose ofthis invention are those in which the amino nitrogen is attached tohydrocarbon groups, preferably alkyl groups, and/ or hydroxy alkylgroups. Suitable modifying agents in addition to those illustrated inthe examples include butylamine, hexanolamine, dipropylamine,dipropanolamine, N-ethylethanolamine, N -propylethanolamine,N-amylethanolamine, N -hexylethanolamine, N- cyclohexylethanolamine,N-propylpropanolamine, N- ethylcyclohexylamine or derivatives, such asortho-methyl- N-methylcyclohexylamine andortho-methyl-N-ethylcyclohexylamine. These contain at least 4 carbonatoms and have no radical of more than 8 carbon atoms. Larger radicals,in addition to decreasing the solubility of the amine, tend to producesurface activity which is not desirable in the process of thisinvention.

For effective results and for the most economic operation, very smallquantities of amine modifiers are used. It is undesirable to use morethan 1 millimole of agent per 100 grams of viscose; the generallypreferred range being from 0.1 to 0.85 millimole per 100 grams ofviscose. The optimum concentration of any given agent depends on itsparticular effectiveness and on its molecular weight. For example,smaller concentrations of N-methylcyclohexylamine will be as effectiveas larger concentrations of cyclohexylamine. The optimum concentrationof modifier in the viscose also depends to some extent on processvariables such as the spinning speed and the level of modifierconcentration maintained in the bath. At the high spinning speeds usedin industrial practice, less agent is desirable than at lower speeds.The amount of agent in the viscose should also be less With higherconcentrations in the bath, but the nitrogen content of the bath shouldnot exceed 200 p. p. m.

In practicing this invention, the viscose spinning solutions areprepared by the split xanthation process. The viscose solutions cancontain from 4 to cellulose and 4 to 8% alkali, preferably 5 to 7%cellulose and 4 to 6.5% alkali. The sum of carbon disulfide used in thetwo xanthation steps can be from to 60% (based on the air-dried pulp).

The split xanthation process, besides being essential in the process ofthis invention, provides several inherent advantages. Split xanthationresults in a shorter xanthation cycle. A reduced xanthation cycleresults in greater productivity for the baratte. Furthermore, since lesscarbon disulfide is used in the baratte, cleaning the baratte, which hadbeen time consuming and difficult, can be performed relatively quicklyand easily. Splitting xanthation also provides more efficient reactionwith carbon disulfide and a reduction in the problem involved inventilating to remove poisonous carbon disulfide.

This invention permits the use of viscose displaying salt indices above5, preferably above 10. The use of higher salt indices means acorresponding decrease in ripening time. Partially ripened and, in somecases, unripened viscoses may be spun by this process. Thus, economiesare effected by shortening the viscose preparation cycle and by reducingthe space required for this operation.

The high tenacity yarns and cords of this invention display outstandingfatigue resistance which is so important in the reinforcement of rubbergoods, such as automobile tires, belts used in commercial operation and10 the like. The abrasion characteristics and durability of the yarnscan be advantageously utilized in preparing textile fabrics ofexceptionally high launderability. These easily launderable fabrics canbe prepared from yarns composed of either continuous filaments or staplefibers.

Since many diiferent embodiments of the invention may be made withoutdeparting from the spirit and scope thereof, it is to be understood thatthe invention is not limited by the specific illustrations except to theextent defined in the following claims.

What is claimed is:

l. A process for spinning modified viscose to provide improved rayonyarns and cords comprising the steps of partially xanthating alkalicellulose with carbon disulfide in a dry phase in the absence of amonoamine modifier to an absolute sulfur substitution value of at least13%, based on the cellulose content, and a relative xanthate sulfursubstitution value of up to based on the absolute value obtained in thefinal xanthation; mixing the partially xanthated alkali cellulose withaqueous caustic solution to a cellulose content of 4% to 15% and acellulose to caustic ratio approximating that of the final viscosesolution; completing the xanthation with carbon disulfide in thepresence of at least about 0.02. but less than 1 millimole of an organicmonoamine modifier per grams of final viscose solution, said organicmonoamine modifier having at least one hydrogen atom attached to theamino nitrogen, containing at least four carbon atoms, having a maximumof eight carbon atoms in any one radical, and being soluble to theextent of at least 0.1% in 6% caustic soda solution; preparing a viscosesolution containing 4% to 10% of cellulose and 4% to 8% of caustic fromthe modified cellulose xanthate mixture; and spinning the modifiedviscose solution into a spinning bath containing 4% to 12% sulfuricacid, about 13% to 25% sodium sulfate, 2% to 15% zinc sulfate and lessthan 200 parts per million of combined nitrogen at 40-80 C.

2. A process as defined in claim 1 in which the organic monoaminemodifier is selected from the group consisting of cyclohexylamine,N-rnethylcyclohexylamine, N-ethylcyclohexylamine, diethylamine,morpholine, namylamine, N-butylethanolamine, diethanolarnine,ethylethanolamine, pyridine, piperidine, ortho-rnethyl-N-methylcyclohexylamine, and ortho-methyl-N-ethylcyclohexylamine.

3. A process as defined in claim 1 in which the amount of organicmonoamine modifier added is from 0.1 to 0.85 millimole of modifier per100 grams of viscose.

References Cited in the file of this patent UNITED STATES PATENTS1,929,868 Haller Oct. 10, 1933 2,393,817 Schlosser et al Jan. 29, 19462,397,454 Woodward Mar. 26, 1946 2,481,692 Schlosser et al Sept. 13,1949 2,535,044 Cox Dec. 26, 1950 2,535,045 Cox Dec. 26, 1950

1. A PROCESS FOR SPINNING MODIFIED VISCOSE TO PROVIDE IMPROVED RAYONYARNS AND CORDS COMPRISING THE STEPS OF PARTIALLY XANTHATING ALKALICELLULOSE WITH CARBON DISULFIDE IN A DRY PHASE IN THE ABSENCE OF AMONOAMINE MODIFIER TO AN ABSOLUTE SULFUR SUBSTITUTION VALUE OF AT LEAST13%, BASED ON THE CELLULOSE CONTENT, AND A RELATIVE XANTHATE SULFURSUBSTITUTION VALUE OF UP TO 90%, BASED ON THE ABSOLUTE VALUE OBTAINED INTHE FINAL XANTHATION; MIXING THE PARTIALLY XANTHATED ALKALI CELLULOSEWITH AQUEOUS CAUSTIC SOLUTION TO A CELLULOSE CONTENT OF 4% TO 15% AND ACELLULOSE TO CAUSTIC RATIO APPROXIMATING THAT OF THE FINAL VISCOSESOLUTION; COMPLETING THE XANTHATION WITH CARBON DISULFIDE IN THEPRESENCE OF AT LEAST ABOUT 0.02 BUT LESS THAN 1 MILLIMOLE OF AN ORGANICMONOAMINE MODIFIER PER 100 GRAMS OF FINAL VISCOSE SOLUTION, SAID ORGANICMONOAMINE MODIFIER HAVING AT LEAST ONE HYDROGEN ATOM ATTACHED TO THEAMINO NITROGEN, CONTAINING AT LEAST FOUR CARBON ATOMS, HAVING A MAXIMUMOF EIGHT CARBON ATOMS IN ANY ONE RADICAL, AND BEING SOLUBLE TO THEEXTENT OF AT LEAST 0.1% IN 6% CAUSTIC SODA SOLUTION; PREPARING A VISCOSESOLUTION CONTAINING 4% TO 10% OF CELLULOSE AND 4% TO 8% OF CAUSTIC FROMTHE MODIFIED CELLULOSE XANTHATE MIXTURE; AND SPINNING THE MODIFIEDVISCOSE SOLUTION INTO A SPINNING BATH CONTAINING 4% TO 12% TO SULFURICACID, ABOUT 13% TO 25% SODIUM SULFATE, 2% TO 15% ZINC SULFATE AND LESSTHAN 200 PARTS PER MILLION OF COMBINED NITROGEN AT 40*-80*C.